Monroe 640 calculator

This is a magnificent desk calculator. It has a multiplexed 16-digit nixie tube display.

On the inside, there are three PCB's: the main board, the display board and a keyboard board. The main board holds three TI IC's. More interesting than the TI logo on the chips is the Canon logo on the PCB's and the text "made in Japan"...

I got this calculator through a barter. The calculator was worked fine right away, as far as I could judge. Because there is no manual, I cannot use all of the functions. I traded the calculator in 2008 to a colector of nixie desk calculators. That gave me more room for my measuring equipment.